Java.lang.NoSuchFieldError: no “I” field “value” in class “Ljava/lang/Integer;” or its superclasses - Android 10

[singhal2]

I understand that the following might not be enough to debug the problem. I am trying to get ideas so as to find a workaround to this problem. Therefore, please do not hesitate to ask for more information. Any help is appreciated.

I have a .so android library which I am integrating into a Xamarin Forms project. The library helps the app connect to an IoT device. As the library methods are of the following signature, I decided to write a java wrapper to simplify the parameters and create an aar file. Afterwards, I natively bind the aar and use it as a dll in my project. I DO NOT have the library source code available, therefore I am unable to debug it further. It is important to note that the problem in Xamarin only occurs when the Compile Target is > 10. Otherwise, it works fine. My guess is that the latest Updates to non-SDK interfaces broke the application.

Method signature:
public static native int ReadParams(String token, StringBuilder serial, StringBuilder ssid, StringBuilder password, StringBuilder sensor, Integer keepAlive);

Call from Java wrapper

StringBuilder strSerial = new StringBuilder();
StringBuilder strssid = new StringBuilder();
StringBuilder strpassword = new StringBuilder();
StringBuilder strsensor = new StringBuilder();
Integer keepAlive = new Integer(0);
//Crash on below line
int response = EPM002Lib.ReadParams(token, strSerial, strssid, strpassword, strsensor, keepAlive);

Stacktrace:

--- End of managed Java.Lang.IncompatibleClassChangeError stack trace ---
java.lang.NoSuchFieldError: no "I" field "value" in class "Ljava/lang/Integer;" or its superclasses
at com.esong.lib.EPM002Lib.ReadParams(Native Method)
at com.sensorwa.config.configdemo.SquareSdkhelper.ReadParams(SquareSdkhelper.java:32)
at crc643f46942d9dd1fff9.ButtonRenderer_ButtonClickListener.n_onClick(Native Method)
at crc643f46942d9dd1fff9.ButtonRenderer_ButtonClickListener.onClick(ButtonRenderer_ButtonClickListener.java:30)
at android.view.View.performClick(View.java:7201)
at android.view.View.performClickInternal(View.java:7170)
at android.view.View.access$3500(View.java:806)
at android.view.View$PerformClick.run(View.java:27582)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7710)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:516)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)

Steps to Reproduce

The error occurs when the above method is called as shown above. I am unsure as to what exactly is the issue here and what's causing it. However, the same aar library works well in a native Android application. Which makes me believe that the issue is in Xamarin Forms.

• Version with issue: 4.8.0.1534
• Last known good version: Android 9 and below
• Platform Target Frameworks:
  • Android: 10
• Affected Devices: Android

Reproduction Link

I cannot provide a sample to reproduce the problem as the error occurs when the connection to the IoT device is made.

Thank you very much.

[jonpryor]

the problem in Xamarin only occurs when the Compile Target is > 10.

What do you mean by this, exactly? Setting $(TargetFrameworkVersion) to v11.0?

Or does it mean setting the //uses-sdk/@android:targertSdkVersion to 30 within AndroidManifest.xml?

Or something else?

More concerning is the stack trace:

java.lang.NoSuchFieldError: no "I" field "value" in class "Ljava/lang/Integer;" or its superclasses
at com.esong.lib.EPM002Lib.ReadParams(Native Method)

com.esong.lib.EPM002Lib.ReadParams isn't Xamarin.Android code; it's from your native library, and the error is probably thrown because the native library is doing the equivalent of:

auto Integer_class = env->FindClass("java/lang/Integer");
auto Integer_value = env->GetFieldID(Integer_class, "value", "I");
// Integer_value is NULL

What I think is happening is that "when the Compile Target is > 10" means "//uses-sdk/@android:targertSdkVersion >= 29", which brings us to Restrictions on non-SDK interfaces: starting with Android 9, Google started preventing the use of Reflection against certain APIs. From the Expected behavior when restricted non-SDK interfaces are accessed documentation:

JNI via env->GetFieldID():
NULL returned, NoSuchFieldError thrown

which is what you're seeing.

In particular, the hiddenapi-flags.csv for Android 10 contains the line:

Ljava/lang/Integer;->value:I,greylist-max-p

which is exactly the member mentioned in the java.lang.NoSuchFieldError.

---

I think the actual solution is that you need to obtain an update to your ".so android library."

[singhal2]

Hello,

Thank you for the detailed explanation. I understand the problem much better now.

I was able to obtain the native library code and as you mentioned the library is indeed doing the following.

	auto clazz = env->FindClass("java/lang/Integer");
	if (clazz == nullptr)
		return;

	auto id = env->GetFieldID(clazz, "value", "I");
	if (id == nullptr)
		return;

	env->SetIntField(integer, id, val);

However, I am unsure as to how do I change the code so as to not use reflection? Do you have some documentation or code example that you could provide, please?

Would it be along the following lines?

jclass cls = (*env)->FindClass(env, "java/lang/Integer");
jmethodID midInit = (*env)->GetMethodID(env, cls, "<init>", "(I)V");
if (NULL == midInit) return NULL;
jobject newObj = (*env)->NewObject(env, cls, midInit, number);

Thanks for all the help

Abhi

[SonNXP]

Hello Singhal2
Do you have a solution for this issue?

[singhal2]

I resolved it by finally changing the source code of the library I was using and recompiled it again. I am not changing the Integer value anymore.